A micro-device for corneal cross-linking treatment includes a body including an outer portion and an inner portion. The outer portion is disposed about a periphery of the inner portion. The inner portion is shaped such that, when the body is positioned against a surface of an eye, the outer portion contacts the surface of the eye and the inner portion defines a chamber over a cornea of the eye. The micro-device includes an illumination system including a micro-optical element coupled to the body. The micro-optical element is configured to direct photoactivating light to the cornea of the eye when the body is positioned against the surface of the eye. The photoactivating light generates cross-linking activity with a cross-linking agent applied to the cornea.